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• avutil/file_open : avoid file handle inheritance on Windows

  29 octobre 2015, par Tobias Rapp

  avutil/file_open : avoid file handle inheritance on Windows
  Avoids inheritance of file handles on Windows systems similar to the
  
  O_CLOEXEC/FD_CLOEXEC flag on Linux.
  Fixes file lock issues in Windows applications when a child process
  
  is started with handle inheritance enabled (standard input/output
  
  redirection) while a FFmpeg transcoding is running in the parent
  
  process.
  Links relevant to the subject :
  https://msdn.microsoft.com/en-us/library/w7sa2b22.aspx
  Describes the _wsopen() function and the O_NOINHERIT flag. File handles
  
  opened by _wsopen() are inheritable by default.
  https://msdn.microsoft.com/en-us/library/windows/desktop/ms682425%28v=vs.85%29.aspx
  Describes handle inheritance when creating new processes. Handle
  
  inheritance must be enabled (bInheritHandles = TRUE) e.g. when you want
  
  to pass handles for stdin/stdout via lpStartupInfo.
  Signed-off-by : Tobias Rapp <t.rapp@noa-audio.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavutil/file_open.c

• Programmatically get non-overlapping images from MP4

  16 novembre 2019, par Carlos F

  My ultimate goal is to get meaningful snapshots from MP4 videos that are either 30 min or 1 hour long. "Meaningful" is a bit ambitious, so I have simplified my requirements.

  The image should be crisp - non-overlapping, and ideally not blurry. Initially, I thought getting a keyframe would work, but I had no idea that keyframes could have overlapping images embedded in them like this :

  Of course, some keyframe images look like this and those are much better :

  

  I was wondering if someone might have source code to :

  Take a sequence of say 10-15 continuous keyframes (jpg or png) and identify the best keyframe from all of them.

  This must happen entirely programmatically. I found this paper : http://research.microsoft.com/pubs/68802/blur_determination_compressed.pdf

  and felt that I could "rank" a few images based on the above paper, but then I was dissuaded by this link : Extracting DCT coefficients from encoded images and video given that my source video is an MP4. Of course, this confuses me because the input into the system is just a sequence of jpg images.

  Another link that is interesting is :

  Detection of Blur in Images/Video sequences

  However, I am not sure if this will work for "overlapping" images.

• Text backdrop by ass formatting

  14 septembre 2024, par Armen Sanoyan

  I want to add box behind a word using ass subtitles formatting. The box should have border radius. the ass file later will be used by ffmpeg.

  


  I have tried the BorderStyle=3 form stack ansers 1, 2 both of them do not provide a way to get rounded boxes. Also the BorderStyle=4 didn't work for me. In comments of last stack answer I found a possible reason that my libraries can be old, but anyway it doesn't seem that BorderStyle=4 will solve my problem of border radius. There is another way to achieve rounded box link to answer. I didn't figure it out how to install all the libs he explained there. Also the later answer seems to me over complicated. Is there an other way to make the borders of box rounded without suffering and pain ? I also tried drawing the box with Drawing commands like

  


  {\p1}m 0 0 s 100 0 100 100 0 100 c{\p0}


  


  But it still doesn't seem to be the best way to achieve rounded borders.